Trade plays a key role in the spread of alien species and has arguably contributed to the recent enormous acceleration of biological invasions, thus homogenizing biotas worldwide. Combining data on 60-year trends of bilateral trade, as well as on biodiversity and climate, we modeled the global spread of plant species among 147 countries. The model results were compared with a recently compiled unique global data set on numbers of naturalized alien vascular plant species representing the most comprehensive collection of naturalized plant distributions currently available. The model identifies major source regions, introduction routes, and hot spots of plant invasions that agree well with observed naturalized plant numbers. In contrast to common knowledge, we show that the 'imperialist dogma,' stating that Europe has been a net exporter of naturalized plants since colonial times, does not hold for the past 60 years, when more naturalized plants were being imported to than exported from Europe. Our results highlight that the current distribution of naturalized plants is best predicted by socioeconomic activities 20 years ago. We took advantage of the observed time lag and used trade developments until recent times to predict naturalized plant trajectories for the next two decades. This shows that particularly strong increases in naturalized plant numbers are expected in the next 20 years for emerging economies in megadiverse regions. The interaction with predicted future climate change will increase invasions in northern temperate countries and reduce them in tropical and (sub)tropical regions, yet not by enough to cancel out the trade-related increase.

Division of Conservation Landscape and Vegetation Ecology University of Vienna Rennweg 14 1030 Vienna Austria Department of Biological Diversity and Nature Conservation Environment Agency Spittelauer Laende 5 1090 Vienna Austria

Division of Conservation Landscape and Vegetation Ecology University of Vienna Rennweg 14 1030 Vienna Austria Department of Biological Diversity and Nature Conservation Environment Agency Spittelauer Laende 5 1090 Vienna Austria Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Private Bag X1 Matieland 7602 South Africa

Ecology University of Konstanz Universitätsstrasse 10 78457 Konstanz Germany

Facultad de Ciencias Forestales Instituto de Ecología y Biodiversidad Universidad de Concepcion Victoria 631 403000 Concepcion Chile

German Centre for Integrative Biodiversity Research Halle Jena Leipzig Deutscher Platz 5e 04103 Leipzig Germany

Institute for Chemistry and Biology of the Marine Environment University of Oldenburg Carl von Ossietzky Straße 9 11 Oldenburg Germany

Institute for Chemistry and Biology of the Marine Environment University of Oldenburg Carl von Ossietzky Straße 9 11 Oldenburg Germany Division of Conservation Landscape and Vegetation Ecology University of Vienna Rennweg 14 1030 Vienna Austria

Institute of Biochemistry and Biology University of Potsdam Maulbeerallee 1 D 14469 Potsdam Germany

Institute of Botany Department of Invasion Ecology The Czech Academy of Sciences Zámek 1 CZ 252 43 Průhonice Czech Republic

Institute of Botany Department of Invasion Ecology The Czech Academy of Sciences Zámek 1 CZ 252 43 Průhonice Czech Republic Department of Ecology Faculty of Science Charles University Prague Viničná 7 CZ 128 44 Prague Czech Republic

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